There has been known a prefilled syringe in which a sterilized syringe outer tube is filled with a liquid product in an aseptic manner (see, for example, Patent Document 1). The prefilled syringe includes: the syringe outer tube having a spout through which the liquid product is ejected and a lock adapter rotatably supported on the spout; and a cap mounted onto the spout of the syringe outer tube and locked by a lock member. When the prefilled syringe described in Patent Document 1 is, in its unused state or in its unopened sealed state, the cap and the lock adapter are collectively covered with a film with a perforation in a state in which the cap is mounted on the syringe outer tube.
When the prefilled syringe in the unused state is unsealed and the cap is detached but the cap is then remounted, i.e., the prefilled syringe is recapped, without using the prefilled syringe, it is impossible to recognize at first glance that the prefilled syringe is in an already unsealed state. When the cap of a prefilled syringe is once opened, it is difficult to maintain the aseptic state inside the prefilled syringe for a long time, and, therefore, the liquid product needs to be used swiftly. If recapping is done as above-mentioned, however, there has been a problem that the recapped prefilled syringe which is low in asepticity may be put to use, while erroneously deeming it as in the unused state.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-315827